1. Field of the Invention
The present invention relates to a process for producing a polymer and in particular to a process for producing a polymer such as styrene type polymer, olefin type copolymer etc. having a high degree of a syndiotactic structure efficiently with high activity.
2. Description of the Related Arts
Recently, a catalyst consisting of a transition-metal compound particularly a titanium compound and methylaluminoxane is used to polymerize a styrene type monomer to obtain a styrene type polymer with a syndiotactic structure (also referred to herein after as "SPS") (Japanese Patent Laid-Open Publication No. 187,708/1987).
In the production of a styrene type polymer as described above, it is also proposed that a coordination complex compound consisting of an anion or a cation having a plurality of groups bound to a metal is used to produce a styrene type polymer with a syndiotactic structure efficiently without using aluminoxane which is expensive and used in a large amount (Japanese Patent Laid-Open Publication Nos. 415,573/1990 and 415,574/1990).
It is further proposed that in the production of a styrene type monomer, an alkylating agent and a reaction product between water and a straight-chain alkyl aluminium whose alkyl moiety has 2 or more carbons are added to decrease the molecular weight of a polymer to be formed without reducing polymerization activity (Japanese Patent Laid-Open Publication No. 316,215/1995).
Activity expression is conventionally not sufficient in the polymerization of a styrene type monomer when the catalyst consisting of a titanium compound and aluminoxane as described above is used, and it is therefore necessary to employ an excess amount of aluminoxane in order to improve activity. In such case, however, a large amount of metals remain in the resulting polymer and if left as it is, there will occur bad influences such as deterioration of the mechanical properties of the polymer, which makes a high degree of technical skill essential for post-treatment. Further, even if an excess amount of aluminoxane is used, there is another problem that the activity does not exceed a certain level. If aluminoxane is not used and a coordination complex compound consisting of an anion or cation having a plurality of groups bound to a metal is used, the amount of metals in the resulting polymer can be reduced, but low activity is the problem. Therefore, it is desired to develop a production process in which a polymer can be obtained with high catalyst activity in case these catalyst systems are used.